Fabry-Perot sensors have broad utility for applications where the measurement of the absolute length of an interferometric gap in a Fabry-Perot sensor. These gaps may relate to pressure, temperature, strain or some other physical property of the material which bounds one side of the gap. For example, their simplicity of design allows these sensors to be embedded into large industrial applications including gas turbines, pressure vessels, pipelines, buildings, or other structures, in order to provide information about pressure, temperature, strain, vibration, or acceleration within the structure. Their size, durability and fast response time make these sensors advantageous.
In operation, Fabry-Perot interferometers are capable of spanning a range of gaps to create an interference pattern, regardless of whether via reflected light or transmitted light. Performing an optical cross-correlation of such an interference pattern, by reflecting or transmitting the interference pattern through a second interferometer, produces a distinctive signal that reaches a peak intensity of light when the length of the gap in the optical cross-correlator matches the length of the gap in the Fabry-Perot sensor. This distinctive peak intensity signal forms the basis for measurement of the absolute length of a gap in the Fabry-Perot sensor. Although previous systems known to the inventors use optical cross-correlators to make measurements of the length of gaps in Fabry-Perot sensors, the invention described herein is capable of making quantitative, absolute measurements with better sensitivity, greater dynamic range, greater frequency response, and lower cost than previously known systems.